Composition of alkylidene bisacrylamide and ethylenic monomers with calcium chloride



1965 D. R. HOLBERT ETAL 3,210,310

COMPOSITION OF ALKYLIDENE BISACRYLAMIDE AND ETHYLENIC MONOMERS WITHCALCIUM CHLORIDE Original Filed July 9, 1959 2 Sheets-Sheet 1 ATTORNEYSD. R. HOLBERT ETAL 3,210,310 COMPOSITION OF ALKYLIDENE BISACRYLAMIDE ANDETHYLENIC MONOMERS WITH CALCIUM CHLORIDE Original Filed July 9, 1959 2Sheets-Sheet 2 United States Patent 3 Claims. c1. 260-29.7)

This application is a division of our application Serial No. 826,049,filed July 9, 1959.

This invention relates to weighted liquid resin-forming compositions andmore particularly is concerned with compositions including alkylidinebisacrylamide, an ethylenic monomer and calcium chloride. Theseresinforming materials have particular utility in the well treatingfield, e.g. processes which combat the obstruction of gas circulation ingas drilling wells through permeable subterranean formations and of theprocesses which partially or completely plug permeable subterranean wellareas.

An oxidation-reduction catalytic polymerization system, e.g., anammonium persulfate-nitrilotrispropionamide system has been added to theliquid resin-forming material near the well site prior to placing thematerial in the desired location within the well bore. The components ofa catalytic system of this type are generally added in amounts toprovide initiation of polymerization of the resin-forming material aftera predetermined time, e.g., 30 to 90 minutes, has elapsed in order toprovide sufiicient working time for a proper placement of this materialin the well bore. The polymerization of the material after placement inthe proper position in the well bore should not be too slow such thatany existing turbulances in the well bore will move the material out ofposition and thus critically curtail its sealing effect. Moreover, whenusing the resin-forming material in some well plugging processes, thematerial should be heavy enough to sink in the salt water and sit on thebottom of the well. Salt water generally has a specific gravity greaterthan 1, generally at least about 1.18. Thus, the resin-forming materialshould be sufficiently weighted such that it can be efficientlydisplaced into the permeable area before it can be dispersed by the saltwater or fresh water if any be present. To reduce the chances of thishappening, resinforming materials having specific gravities greater than1.18, preferably greater than 1.5 are desirable.

The present invention is directed to liquid resin-forming compositionssuitable for use in the well-treating field in exhibiting advantageousspecific gravity characteristics for use in processes employing suchmaterials in well bores. This is accomplished by including significantamounts of calcium chloride in the compositions. Calcium chloride ishighly desirable in this respect since unlike sodium chloride, forexample, it will not precipitate or unduly prolong the induction period,i.e. the time required for the catalyst to produce enough free radicalsto initiate the polymerization, particularly after the resinformingmaterial has been placed in position down the hole.

The liquid resin-forming compositions of the present invention areparticularly suitable for use in the well bore treating field andinclude an aqueous solution of an alkyl- 3,2103 10 Patented Oct. 5, 1965idene bisacrylamide, an ethylenic comonomer, and calcium chloride, thebisacrylamide having the formula:

is a hydrocarbon residue of an aldehyde containing, for instance, fromabout 1 to 10 and preferably from about 1 to 5 carbon atoms, e.g.,formalde-, aceta1de-, and valeraldehyde; but usually about 1 to 3 carbonatoms; and R is a member of the group consisting of hydrogen and amethyl radical. W

The other comonomer is a solid, liquid or gaseous ethylenic (i.e.,contains at least the C=C radical) compound with a solubility of atleast about 2 percent by weight, and preferably at least about 5percent, in water and which copolymerizes with the aforesaidbisacrylamide in an aqueous system. Although not essential in practicingthe invention, it is preferred to select an ethylenic comonomer which ispreferably soluble or at least selfdispersible in water with appropriatestirring, as such, for example, methylene-bisacrylamide, which iscapable of polymerizing.

In addition to the comonomer N,N'-methylerebisacrylamide set out in theexamples hereinafter, any of the alkylidene bisacrylamides correspondingto the above formula which are described and claimed in Lundberg PatentNo. 2,475,846 hereby incorporated by reference, or mixtures thereof maybe used as cross-linking agents. Only slight solubility is required ofthe alkylidene bisacrylamide in view of the small amount used;therefore, this component may have a Water solubility as low as about0.02 percent by Weight at 20 C. but a solubility of at least about 0.10percent is more desirable for general purposes.

A wide variety of ethylenic comonomers or mixtures thereof arecopolymerizable with the alkylidene bisacrylamides; those having aformula containing at least one C=C group, preferably containing fromabout 1 to 8 carbon atoms, hereinafter referred to as the ethenoidgroup, and having appreciable solubility in water are suitable for usein the present invention. See US. Patent No. 2,801,985, herebyincorporated by reference. As set forth in this patent, theunsubstituted bonds in the ethenoid group may be attached to one or moreof many different atoms or radicals including hydrogen, halogens, suchas chlorine and bromine, cyano, aryl, aralkyl, alkyl, and alkylene withor without solubilizing groups attached to these hydrocarbons. Inaddition, the substituents on the ethenoid group may comprise one ormore hydrophilic groups including formyl, methylol, polyoxyalkyleneresidues and quaternary ammonium salt radicals,

OOCH; OOCCH -SO X, where X is H, NH an alkali metal or an alkylamine;-CONR and -CH CONR where each R is hydrogen, alkylol, lower alkyl or apoly- 3 oxyalkylene radical; and -COOR' and -CH COOR', where R is a H,NH alkali metal, alkaline earth metal, organic nitrogenous base,alkylol, lower alkyl or polyoxyalkylene radical. The large number ofcombinations and proportions of the various suitable substituents makesit impractical to list all compounds in this category which may beemployed. The water solubility of these substances is known to dependchiefly on the number and type of hydrophilic and hydrophobic radicalstherein; for example, the solubility of compounds containing an alkylradical diminishes as the length of the alkyl chain increases and arylgroups tend to decrease water solubility whereas the aforesaidhydrophilic substituents all tend to improve the solubility of a givencompound in water. Accordingly, the comonomer should be selectedaccording to chemical practice from those containing suflicienthydrophilic radicals to balance any hydrophobic groups present in orderto obtain the requisite water solubility of monomer.

Among the water-soluble ethenoid monomers, those containing an acrylylor methacrylyl group are especially recommended. These are exemplifiedby N-methylol acrylamide, calcium acrylate methacrylamide andacrylamide. Other suitable ethanoid compounds are acrylic acid; otherN-substituted acrylamides, such as N-methylacrylamide, N 3hydroxypropylacrylamide, dimethylaminopropylacrylamide, N-ethylolacrylamide; acrylonitrile; saturated alkyl esters of acrylic acid, i.e.methyl acrylate, fl-hydroxyethyl acrylate; ethylene glycol andpolyethylene glycol acrylates, an example being the reaction product offi-hydroxyethylacrylate or acrylic acid with about 1 to about 50 mols ormore of ethylene oxide; salts of acrylic acid, i.e., magnesium acrylate,sodium acrylate, ammonium acrylate, zinc acrylate,fl-aminoethylacrylate, B-methylaminoethylacrylate, guanidine acrylateand other organic nitrogenous base salts, such as diethylamine acrylateand ethanolamine acrylate; quaternary salts like alkyl acrylamidopropyldimethylamino chloride; acrolein, fl-carboxyacrolein, butenoic acid;a-chloroacrylic acid; fl-chloroacrylic acid; as well as methacrylic acidand its corresponding derivatives.

Maleic acid and its corresponding derivatives including partial esters,partial salts, and ester salts thereof; maleamic, chloromaleic, fumaric,itaconic, citraconic, vinyl sulfonic, and vinyl phosphonic acids andtheir corresponding derivatives and mixtures thereof. Derivatives ofthis kind and other suitable compounds include a,B-dichloroacrylonitrile, methacrolein, potassium methacrylate, magnesiummethacrylate, hydroxyethyl methacrylate, zinc fl-chloroacrylate,trimethylamine methacrylate, calcium ,B-chloromethacrylate, diethylmethylene succinate, methylene succindiamide, monomethyl maleate, maleicdiamide, methylene maloanamide, diethyl methylene malonate, methylisopropenyl ketone, ethyl vinyl ketone, propyl vinyl ketone, vinylformate, vinyl lactate, vinyl acetate, vinyl bromoacetate, vinylchloroacetate, vinyl pyrrolidone, allyl levulinate, allyl alcohol,methallyl alcohol, diallyl carbonate, allyl lactate, allyl gluconate,di([i-aminoethyl) maleate, di(methylaminoethyl) maleate,di(N,N'-dimethyl-B-aminoethyl) maleate, sulfonated styrene, vinylpyridine, maleic anhydride, sodium maleate, ammonium maleate, calciummaleate, monopotassium maleate, monoammonium maleate, monomagnesiummaleate, methyl vinyl ether, N-aminoethyl maleamide, N-aminoethylmaleimide, alkyl aminoalkyl maleamides, N-vinyl amines, N-allyl amines,heterocyclic ethenoid compounds containing nitrogen in a tertiary aminogroup, and the amine and ammonium are salts of said cyclic compounds,N-vinyl acetamide, N-vinyl-N-methyl formamide,N-vinyl-N-methyl-acetamide, N-vinyl succinimide, N-vinyl diformamide,N-vinyl diacetamide, vinyl sulfonyl chloride, vinyl sulfonic acid salts,vinyl sulfonic acid amides, vinyl oxazolidone, allyl amine,diallylamine, vinyl methyl pyridinium chloride, and allyl trimethyl ammonium chloride to name only a few of the operative compounds.

The preferred resin-forming composition of the present invention is inan aqueous medium and has an initial viscosity approximating that ofwater. These compositions can be formed by dissolving a mixture ofacrylamide and N,N'-methylenebiscarylamide in fresh water. Generally,this mixture contains about 1 to 25 weight percent ofN,N'-methylenebisacrylamide and about 99 to weight percent ofacrylamide. The aqueous solution will usually include from about 5weight percent of this mixture to its limit of solubility and preferablythis amount is about 5 to 25 percent while the CaCl will generallycomprise from about 15 to 30 weight percent and preferably from about 25to 30 weight percent on the basis of the water. Although the acrylamideas such is preferred, its nitrogen atom could be substituted as with ahydroxy methyl or a hydroxy ethyl group.

In addition to the above-mentioned ingredients, the compositions mayinclude other components, particularly when they are destined for usedown well holes, e.g. in processes for plugging permeable well areas.For instance, compounds exhibiting catalytic activity or other weightingagents may be added. Components exhibiting catalytic activity can beadded prior to injection of the compositions in the well bore. Care mustbe exercised as to the amount of catalytic material added and this willdepend upon the specific component employed, however, this amount shouldbe such that sufficient Working time is provided to permit displacementof the composition into the permeable area to be plugged before ithardens into the solid or semi-solid state. In general, the working lifeof the material at the temperatures and pressures encountered in thebore hole is such that it has a viscosity of up to about 10 to 15centipoises, advantageously about 1 to 5 centipoises, at theseconditions for at least about 15 minutes, and preferably for at leastabout 30 minutes. When referring to working life we mean the time whichelapses after all essential ingredients for the formation of the solidor semi-solid plugging resin or plastic under the conditions oftemperature and pressure found in the area of the well bore to beplugged have been added, for instance monomer, catalyst and promoter,e.g., a redox catalyst system, etc. A redox catalyst system generallyincludes an oxidizing agent, i.e., the catalyst, and reducing agent,i.e., promoter. The oxidizing component of the redox catalyst system caninclude for instance, any of the usual Water-soluble peroxy catalystsderived from per-acids such as persulfuric, perchloric, perboric, andpermanganic and their salts. For example, ammonium, potassium and sodiumpersulfates, hydrogen peroxide, the alkali metal and ammoniumperchlorates and the like may be employed. Among the reducing componentsthat can be employed are the oxygen-containing sulfur compounds such asthe alkali metal, e.g., sodium or potassium, bisulfites, andnitrilo-trispropionamide. Examples of typical oxidizing agent-reducingagent combinations are sodium per-sulfate, potassium persulfate, orammonium persulfate-nitrilo-trispropionamide. Ammonium persulfate is anacceptable oxidation agent or catalyst to polymerize the aqueous mixtureand it can be employed with a promoter or reducing agent such as sodiumthiosulfate or nitrilo-tris-propionamide. The amounts of each of thecatalyst and promoter usually are about 0.1 to 2 weight percent based onthe aqueous solution of resin-forming material, and these amounts can bevaried to give the desired working life. For instance, a weight ratio ofcatalyst to promoter of 1 to 2 in an aqueous solution containing 20weight percent of the acrylamide and N,N-methylenebisacrylamide percentacrylamide and 5 percent N,N'-methylenebisacrylamide) will give aworking life at 70 F. of about 60 to minutes when the catalyst pluspromoter is about 0.5 to 1.5 percent of the aqueous solution.

As to using the weighted composition in some Well plugging processesunless the material is heavy enough to sink below the salt water whichhas a specific gravity greater than 1, generally about 1.05 to 1.2, itmust be quickly displaced into the permeable area before it can disperseinto the salt water phase or an overlying fresh water layer, if any bepresent. To reduce the chances of this happening, weighted resin-formingmaterials of the present invention having advantageous specificgravities, e.g. greater than about 1.2, preferably greater than about1.3 can be used. The specific gravity of the resinforming material canbe adjusted by the addition of varying amounts of calcium chloride.Suitable weighting agents which can be used in combination with calciumchloride include Watereoluble, non-ionizing organic compounds, e.g.,sugar and glycerol. The weighted compositions can be electricallyconductive to distinguish it from other materials present in the wellbore, for instance, brine. Accordingly, with the use of electricalconductivity detection means, the composition can be tracked andpositioned at desirable locations in the well bore when employed in wellplugging processes.

The compositions of the present invention can be used in a method forcombatting the effect of a reduction or a cessation of the aircirculation in air-drilling methods when drilling through permeableareas from which gas, liquid or loosely consolidated strata enters thewell bore being drilled. The desired result is accomplished byselectively and substantially completely sealing formations of thischaracter from the well bore in an expeditious and economical manner soas to maintain the advantages of the air-drilling procedures over theconventional procedures which use mud as the circulating medium.

According to this method, when an obstruction of air circulation, i.e.,a reduction or cessation thereof, is experienced during an air-drillingoperation and the obstruction is attributed to the ingress of gas,liquid or loosely consolidated earth particles into the bore from anadjacent stratum, resin-forming material is introduced into a string oftubing extending downwardly below the permeable formation. The resinousmaterial is conducted downwardly in the tubing. A first portion of theresinous material is conducted through the lower extremity of the tubingand forms a column in the annular space between the tubing and the wallof the well bore which column at least covers the formation to besealed. The level of this annular column is maintained while the upperlevel of the remaining or secondary portion of the resinous material inthe tubing is pressured to force permeable formation sealing amounts ofresinous material into the permeable formation. The resinous material ismaintained in this position until it substantially solidifies. continuedwith gas circulation to remove cuttings from the well.

This material is of the type that will harden at temperaturesencountered in the well bore, which in many cases are between about 50to 200 F. The quantity of resin-forming material used must be adequateto extend horizontally into the formation of ingress for a distancesufiicient to securely seal this formation subsequent to the hardeningof the resinous material to prevent further ingress of unwantedextraneous materials. This distance usually extends at least about sixinches into the formation. Moreover, in this method it is imperativethat the resin-forming composition occupy the well bore adjacent theformation of ingress when the hardened resin is formed. Accordingly,after the introduction of the resinforming composition, which has aspecific gravity higher than the ingressing well fluid, into the wellbore detection means are employed to track the upper level of theresinforming composition, and gas or liquid, e.g. air or water pressureis applied to bring this upper level approximately adjacent the upperlevel of the strata of ingress, and the resinous composition ismaintained in this position until it solidifies. Although air, other gasor liquid pressure can be employed in our method, air is preferablysince (a) it permits better control of the resin-forming material, and

The solid resin is drilled through and drilling is depend upon thenature of the obstruction encountered and the depth of the permeableformation; it is generally greater than about 150 p.s.i. but is usuallyabout 150 to 1000 p.s.i. Since tremendous pressures can be required, itmay be desirable to produce such pressures by employ ing liquid and gasin combination, e.g., provide a liquid column above the resin-formingcomposition and exert air pressure on the liquid column. Followingsolidification of the resinous composition, air-drilling is resumed. Inthe stinger arrangement the stinger itself can be used as an integraldetection unit.

The following specific examples will serve to illustrate my inventionbut is not to be considered limiting.

EXAMPLE I Composition preparation To a liter of water under ambientconditions are added 10 weight percent (100 grams) of a resin-formingcomponent including percent of acrylamide and 5 percent ofN,N'-methylenebisacrylamide, 25 weight percent (250 grams) calciumchloride. This resin-forming composition has a specific gravity higherthan the specific gravity of salt water and a pH of 5.8, and issuitable, for example, for placement into a permeable subterranean wellbore area. The weight percents throughout the specification, unlessotherwise specified, are on the basis of the water.

This composition is mixed with 0.25 gram of ammonium persulfate and 0.5gram of nitrilo-tris-propionamide in 500 cc. of water and has an initialviscosity (1.3 centipoises) approximating that of water (which is about0.5 to 1.5 centipoises under the conditions in many well bores) and isnot greater than about 2.0 centipoises over its working life tofacilitate its placement in the desired well area. At a temperature ofF., it polymerizes in 9 minutes.

EXAMPLE II The compositions of this invention as used in an airdrillingmethod can best be described with reference to a specific example andthe drawing. FIGURES 1 through 10, in which several distinct phases ofthe method are illustrated.

Referring to the drawing, FIGURE 1, the numeral 10 represents the earthssurface through which a well bore 12 is being drilled to anoil-producing formation with rotary drill pipe 14 containing a rotarybit 16 at the lower end. Pressurized air is introduced into drill pipe14 at the surface of the earth, is conducted downwardly therein, existsthrough opening 15 of rotary drill bit 16 at the site or formation ofdrilling 18, and passes upwardly through annulus 20, surrounding drillpipe 14, carrying relatively small as well as larger rock particles fromthe site of drilling to the earths surface.

In FIGURE 2 rotary drill bit 16 passes through crevices 100, andpenetrates a salt water formation 22 at its upper level 24 as indicatedby a reduction in air circulation as well as the muddy nature of theparticles recovered from the site of drilling. The depth of the drillbit is noted and thus the position of upper level 24 of salt waterformation 22 is known. In FIGURE 3 drilling is continued through thesalt water-bearing formation containing crevice 101, air circulationeventually ceases due to the back pressure of the salt water, a columnof salt water 28 rises in the well bore and drill pipe to level 30 inannulus 20 and upper level 31 in drill pipe 14, the lower level 26 ofsalt water formation 22 is penetrated by rotary drill bit 16 anddrilling is discontinued. Occasionally, in cases where the waterformation is of considerable depth, it may not be possible to penetratethe lower level of the formation before water production stops furtherdrilling.

A small amount, e.g. 10 gallons, of radioactive fluid, e.g. aqueousiodine 131 solution is injected into drill pipe 14 and is shown atposition 42. A detecting device 32 consisting essentially of aGeiger-counter is inserted to locate the radioactive fluid.

In FIGURE 4 gas pressure is applied to the liquid column in drill pipe14 to move the upper level 44 of the column of radioactive liquid 42downwardly in the drill pipe to the position shown. As the column movesdownwardly salt water exits through opening 15 of rotary drill bit 16and forms annular salt water column 48 with an upper level 50 in theannular space formed between the drill pipe and the walls of the wellbore. An amount of resinous material at least sufficient to cover theportions of formation 22 exposed to well bore 12, for instance, fiftygallons of resinous material, weighted, e.g. with 25% CaCl to be heavierthan the salt water in the well bore, consisting essentially of 20weight percent of a mixture of N,N-methylene-bis-acrylamide and 95%acrylamide, and 25% CaCl in water, along with 0.3 weight percent ofammonium persulfate and 0.6 weight percent of nitrilo-tris-propionamideis injected down drill pipe 14 at a rate of 2 gallons per minute andpositioned in tubular area 36 located above upper level 44 of theradioactive liquid. Detecting device 32 is used to locate the positionof radioactive liquid 42. A second radioactive isotope layer 43, e.g. ofiodine 131, is added on top of the resinous material.

In FIGURE 5, pressurized air is introduced downwardly in drill pipe 14and moves the resinous material, preceded by radioactive material 42,through opening 15 and up the annulus formed between the drill pipe andthe well bore walls to form an annular column of resinous material 52(with an upper level 54) covering the portions of salt water formation22 exposed in the well bore. In this operation, the pressure of theresinous material is sutficient to force a significant quantity into theadjacent formation and the resinous material displaces annular saltwater column 48 upwardly to new level 50'. As the annular resinousmaterial column 52 is moved upwardly, radioactive material 42 islocated, thus upper level 54, with device 32 which is located withindrill pipe 14, to insure upward movement of upper level 54 of theresinous material at least adjacent and preferably a short distancebeyond the upper level 24 of salt water formation 22. By noting thedepth of the device 32 the position of upper level 54 is known. Annulus20 is sealed at the surface with casing head 21 and air pressure up tothe limit of the surface casing is used to maintain upper level 54 ofannular column of resinous material 52 in the position shown. Detectingdevice 32 is raised (not shown) to locate layer 43 thus upper level 56of the secondary column (tubular) of resinous material 58.

In FIGURE 6 pressurized air (250 p.s.i.) is introduced downwardly indrill pipe 14 and forces resinous material through opening 15 and causesthe simultaneous injection of resinous material in area 62 into theentire portion of permeable formation 22 exposed in the well bore asshown by the indicating arrows. During this phase layer 43 thus upperlevel 56 of resinous material tubular column 58 is tracked with device32.

In FIGURE 7 the displacement of resinous material by air is discontinuedwhen the upper level 56 of resinous material tubular column 58 isapproximately even with upper level 54 of annular resinous materialcolumn 52 as determined by observing the depth of tracking device 32 anddiscontinuing the displacement when the device 32 reaches the depthpriorly noted for upper level 54. In FIGURE 8 the drill pipe and bit arelifted as shown. The well is shut in and the resinous materialsmaintained in this position by regulating the air pressure in both theannulus and drill pipe until the resinous material commences topolymerize. However, the drill pipe can be raised above the resinousmaterial before polymerization time and solidification of the resin asshown in FIGURE 9. The resinous material is copolymerized to a semisolidgel in about 90 minutes although copolymerization time can be controlledby changing the concentration of the catalyst or by adding small amountsof potassium ferricyanide to delay polymerization. In FIGURE 10,following the solidification of the resinous material, air pressure isdiscontinued, detection device 32 is removed, the salt water is blownout, air circulation down drill pipe 14 to rotary drill bit 16 isinitiated, drilling is resumed, the solidified resinous material isdrilled-through, and the drilling continues downwardly into the earthssurface while removing cuttings from the Well bore by air circulationdown the drill pipe and up the well annulus.

It is claimed:

1. A weighted, aqueous solution of a resin-forming material consistingessentially of water, from about 5 weight percent to its limit ofsolubility of a mixture of about 1 to 25 weight percent ofN,N-methylenebisacrylamide, and about to 99 weight percent ofacrylamide, and a redox catalyst system, said aqueous solution includingfrom about 15 to 30 weight percent of calcium chloride based on thewater.

2. The composition of claim 1 wherein the redox catalyst system includesnitrilotrispropionamide as a reducing component.

3. The composition of claim 2 wherein the redox catalyst system includesammonium persulfate as an oxidizing component.

References Cited by the Examiner UNITED STATES PATENTS 2,073,413 3/37Cross 2528.5 2,279,262 4/42 Edwards 16629 2,801,985 8/57 Roth 260-412,805,722 9/57 Morgan et al 2528.55 2,837,492 6/58 Stanton et al.260-296 2,963,457 12/60 Miller 260-29.6

MURRAY TILLMAN, Primary Examiner.

LEON J. BERCOVITZ, WILLIAM H. SHORT,

Examiners.

1. A WEIGHTED, AQUEOUS SOLUTION OF A RESIN-FORMING MATERIAL CONSISTINGESSENTIALLY OF WATER, FROM ABOUT 5 WEIGHT PERCENT TO ITS LIMIT OFSOLUBITLITY OF A MIXTURE OF ABOUT 1 TO 25 WEIGHT PERCENT OFN,N''-METHYLENEBISACRYLAMIDE, AND ABOUT 75 TO 99 WEIGHT PERCENT OFACRYLAMIDE AND A REDOX CATALYST SYSTEM, SAID AQUEOUS SOLUTION INCLUDINGFROM ABOUT 15 TO 30 WEIGHT PERCENT OF CALCIUM CHLORIDE BASED ON THEWATER.